Studies of flammability in turbulent flows using laser Raman spectroscopy

This paper describes the measurement of turbulent concentration parameters using a laser Raman spectrometer. Autocorrelation and probability analysis are applied to investigate the concentration field of a turbulent free jet of natural gas having a Reynolds number of 16000. Results of mean and rms concentration are presented along the jet axis; the asymptotic value of volume fraction fluctuation intensity was found to be ∼30%. A method for obtaining the probability density function is described; this was found to be approximately gaussian on the centre line but highly non-gaussian in off-axis intermittent regions. This information is combined with simplified chemical kinetics to calculate factors relating to ignition probability in such turbulent mixing flows.